Electrical stimulation techniques have become increasingly popular for the treatment of neurological disorders. It has been described to treat movement disorders (U.S. Pat. No. 5,833,709; U.S. Pat. No. 6,094,598; U.S. Pat. No. 6,356,784; U.S. Pat. No. 6,366,813; U.S. Pat. No. 6,484,059); chronic pain (U.S. Pat. No. 6,505,078); epilepsy (U.S. Pat. No. 5,978,702; U.S. Pat. No. 5,800,474); psychiatric disorders (U.S. Pat. No. 6,609,030; U.S. Pat. No. 6,418,344); and to improve cognitive functions (U.S. Pat. No. 5,938,688; U.S. Pat. No. 6,539,263).
Typically, these stimulation techniques involve the implantation of a signal generator and an implantable electrode, optionally coupled to a sensor. The electrode is implanted in the brain, or over the cortical surface, so that the stimulation portion lies adjacent to a predetermined target. The signal generator is operated to deliver electrical pulses through the electrode at a predetermined rate and amplitude. Stimulators in current clinical use deliver electrical stimulation at a fixed rate (0-185 Hertz) with a programmed duty cycle.